Large samples of Monte Carlo (MC) simulated events are used to optimize the event selection criteria, estimate the background contaminations and determine the selection efficiencies. The MC samples are generated using a geant4-based [1]} simulation software package BESIII object oriented simulation tool (BOOST) [2]}, which includes the description of geometry and material, the detector response and the digitization model, as well as tracking for the detector running conditions and performances.
'Inclusive' MC samples of \(1225\times 10^{6}\)  \(J/\psi \)  and \(506\times 10^{6}\)  \(\psi (3686)\)  generic decay events are generated to study the backgrounds.
In the simulation, production of the \(\psi \)  resonances is simulated with the kkmc [3]} generator, while the decays are generated by evtgen [4]} for the known decay modes, setting the branching fractions according to the Particle Data Group (PDG) [5]}, or lundcharm [6]} for the remaining unknown decays.
The QED Final State Radiation (FSR) effect is simulated with photos [7]}.
Signal samples \(\psi \rightarrow D^{0}e^+e^-\)  of \(2.0 \times 10^{5}\)  events are generated according to a theoretical calculation based on the vector meson dominance (VMD) model [8]}, where \(e^+e^-\)  is generated from a virtual photon decay.
